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| Untersuchte Arbeit: Seite: 3, Zeilen: 1-19 (komplett) |
Quelle: Delcenserie et al 2008 Seite(n): 38, Zeilen: left col. 50-62 - right.col. 1ff. |
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| [B cells contribute to the immune response by secreting antibodies] (humoral immunity), whereas T cells act primarily in cell-mediated immunity. T cells can be subdivided into T helper cells (CD4+, T cells expressing CD4 are known as CD4+ T cells) and T cytotoxic cells (CD8+, T cells expressing CD8 are CD8+ T cells ) (Dent and Kaplan 2008; Konig et al 2002).
[Figure A: Antigen presentation stimulates T cells to become either "cytotoxic" CD8+ cells or "helper" CD4+ cells.] B cells recognize their antigens via their BCR. T cells cannot recognize the antigen without some assistance. The antigenic determinant must be presented by an appropriate major histocompatibility complex (MHC) molecule. Thus, they recognize their antigens through their TCR in the form of an MHC/ peptide complex. CD8+ T cells “see” their antigens in the form of a peptide/MHC class I complex, whereas CD4+ T cells recognize their antigens as a peptide/MHC class II complex. MHC class I molecules are expressed at the surface of all nucleated cells, whereas MHC class II molecules are expressed only by professional antigenpresenting cells (APCs), such as dendritic cells (DCs) (Cruz, Jr. and Bergstresser 1990). It is important to note that the cells of the innate immune system are critical to the initiation of the adaptive immune response. Thus, APC activation is the first step in the induction of adaptive immunity. DCs generally absorb antigens from the environment, and once they are activated (mostly by microbial compounds), they mature and migrate to the adjacent lymphoid tissue. To be activated, T cells must not only recognize their specific antigen in the form of a peptide/MHC complex, they also need a costimulation signal that is provided by the activated APCs (Joffre et al 2009). Cruz,P.D., Jr., Bergstresser,P.R., 1990. Antigen processing and presentation by epidermal Langerhans cells. Induction of immunity or unresponsiveness. Dermatol. Clin. 8, 633-647. Dent,A.L., Kaplan,M.H., 2008. T cell regulation of hematopoiesis. Front Biosci. 13, 6229-6236. Joffre,O., Nolte,M.A., Sporri,R., Reis e Sousa, 2009. Inflammatory signals in dendritic cell activation and the induction of adaptive immunity. Immunol. Rev. 227, 234-247. Konig,R., Shen,X., Maroto,R., Denning,T.L., 2002. The role of CD4 in regulating homeostasis of T helper cells. Immunol. Res. 25, 115-130. |
B cells contribute to the immune response by secreting antibodies (humoral immunity), whereas T cells act primarily in cell-mediated immunity. T cells can be subdivided into T helper cells (CD4+, also called Th) and T cytotoxic cells (CD8+). B cells recognize their
antigens via their BCR. T cells cannot recognize the antigen without some assistance. The antigenic determinant must be presented by an appropriate major histocompatibility complex (MHC) molecule. Thus, they recognize their antigens through their TCR in the form of an MHC/ peptide complex. CD8+ T cells “see” their antigens in the form of a peptide/MHC class I complex, whereas CD4+ T cells recognize their antigens as a peptide/MHC class II complex. MHC class I molecules are expressed at the surface of all nucleated cells, whereas MHC class II molecules are expressed only by professional APCs. Dendritic cells (DCs) are the major APCs, and they play a critical role in the initiation of the adaptive immune response. Macrophages and B lymphocytes can also act as professional APCs. It is important to note that the cells of the innate immune system are critical to the initiation of the adaptive immune response. Thus, APC activation is the first step in the induction of adaptive immunity. DCs generally absorb antigens from the environment, and once they are activated (mostly by microbial compounds), they mature and migrate to the adjacent lymphoid tissue. To be activated, T cells must not only recognize their specific antigen in the form of a peptide/MHC complex, they also need a costimulation signal that is provided by the activated APCs. |
Ohne Hinweis auf eine Übernahme. |
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